The present invention relates to a wheel-acting force measuring device for detecting a road surface friction force, a normal counterforce and a road surface friction coefficient, which can be used as a component of either an antilock brake system (ABS) for preventing the locking of wheels on application of the hard brake to a vehicle or a traction control system for preventing excessive slippage of wheels during acceleration.
As for such wheel-acting force measuring device for detecting a load surface friction force, a normal counterforce and a road surface friction coefficient, which can be used as a component of either an antilock brake system for vehicles or a traction control system, various types have heretofore been developed and proposed. However, such known devices require a relative-to-ground velocity sensor or a vehicle deceleration sensor to accurately find the vehicle velocity, making the device complicated and presenting a problem of accuracy. Thus, there has been a need for a device for directly measuring dynamic quantities concerning actions between the road surface and the wheels.
To meet this need, the present applicant proposed, in Japanese Patent Application No. Hei 3-130840, a wheel-acting force measuring device comprising a hole formed in or adjacent an axle, a stress sensor having a strain gauge attached thereto, said stress sensor being fixedly embedded in said hole with its strain gauge oriented in a suitable direction according to an intended stress or load, so that it is capable of directly measuring an optional stress or load occurring in or adjacent the axle.
However, there is a problem that detection signals delivered from the stress detecting sensor are influenced by cross talk according to the selected position of the hole since there are produced in or adjacent the axle a complicated shearing strain accompanying a bending deformation caused by a road surface friction force, a vertical stress and a side force acting on the wheel and a shearing strain accompanying a torsional deformation caused by the brake torque during application of the brake.
In view of such problem, the present invention has for its object the provision of a wheel-acting force measuring device comprising a stress detecting sensor disposed at a stress center axis or stress center point (neutral spot) around the axle acted on by wheel-acting forces from a road surface, so that it is not influenced by cross talk other than road surface friction forces or normal counterforces, and more particularly a wheel-acting force measuring device comprising a hole in or adjacent an axle at a brake caliper angle or an angle close thereto, a stress detecting sensor fixedly embedded in said hole, so that it is not influenced by cross talk, and a wheel-acting force measuring device comprising a hole at a neutral spot free from cross talk, so that the device is not influenced by cross talk.
The present invention provides a wheel-acting force measuring device comprising a hole in or adjacent an axle at a brake caliper angle or an angle close thereto, and a stress detecting sensor fixedly embedded at the position in said hole which coincides with the stress center axle of or adjacent the axle.
In the invention described above, since a hole is formed in or adjacent an axle at a brake caliper angle or an angle close thereto and a stress detecting sensor is fixedly embedded at the position in said hole which coincides with the stress center axis of or adjacent the axle, the cross talk to the output signal from the stress detecting sensor due to the brake torque can be effectively excluded.
The present invention further provides a wheel-acting force measuring device comprising a plurality of holes formed in or adjacent an axle at a brake caliper angle or an angle close thereto, stress detecting sensors fixedly embedded at the positions in said holes which coincide with the stress center axes of or adjacent the axle, wherein the detection signal from each said stress detecting sensor is processed in a signal processing circuit to derive a specified stress.
In this embodiment, a plurality of holes are formed in or adjacent an axle at a brake caliper angle or an angle close thereto and stress detecting sensors are fixedly embedded at the positions in said holes which coincide with the stress center axes of or adjacent the axle, wherein the detection signal from each said stress detecting sensor is processed in a signal processing circuit, thereby making it possible to measure a specific acting force among wheel-acting forces such as a road surface friction force, a normal counterforce and a road surface friction coefficient without being influenced by cross talk due to brake torque.
The present invention yet further provides is a wheel-acting force measuring device comprising a stress detecting sensor fixedly embedded in a spindle or an axle at a position between the brake disk attaching position of a vehicle and the road-contacting surface of a wheel.
in the above invention, a stress detecting sensor is fixedly embedded in a spindle or an axle at a position between the brake disk attaching position of a vehicle and the road-contacting surface of a wheel consequently there occurs less torsional deformation due to brake torque during application of the brake and it is possible to measure outputs such as a road surface friction force and a normal counterforce having almost no cross talk due to brake torque.
The present invention still further provides a wheel-acting force measuring device comprising a stress detecting sensor fixedly embedded in a spindle or an axle at a position between the brake disk attaching position of a vehicle and the road-contacting surface of a wheel at a brake caliper angle or an angle close thereto.
In the present invention described above, since a sensor is positioned at a brake caliper angle or an angle close thereto, there is no torsional deformation due to brake torque during application of the brake and it is possible to measure outputs such as a road surface friction and a normal counterforce having no cross talk due to brake torque.
The present invention still further provides a wheel-acting force measuring device as set forth in any one of Claims 1 through 4, comprising a stress detecting sensor and a signal processing circuit which are simultaneously fixedly embedded in a hole formed in or adjacent an axle at a brake caliper angle or an angle close thereto.
In any of the above wheel-acting force measuring devices, since a stress detecting sensor and a signal processing circuit are simultaneously fixedly embedded in a hole formed in or adjacent an axle at a brake caliper angle or an angle close thereto, there is obtained a high ratio of signal to noise for the output signal from the signal processing circuit.
The present invention still further provides a wheel-acting force measuring device comprising a stress detecting sensor disposed in or adjacent an axle of a vehicle or around an axle subjected to wheel-acting forces and on a stress center axis capable of excluding cross talk other than load surface friction forces or normal counterforces or a stress center axis capable of minimizing the amount of cross talk.
In this wheel-acting force measuring device, since a stress detecting sensor is disposed in or adjacent an axle of a vehicle or around an axle subjected to wheel-acting forces and on a stress center axis capable of excluding cross talk other than load surface friction forces or normal counterforces or a stress center axis capable of minimizing the amount of cross talk, it is possible to measure outputs such as a road surface friction force and a normal counterforce with cross talk other than the road surface friction force and normal counterforce.
In any of the above mentioned wheel-acting force measuring device wherein the strain gauge of the stress detecting sensor may be preferably disposed at an angle of approximately 45 degrees with respect to the horizontal and vertical stress center axes of or adjacent the axle.
Further, in any of the above wheel-acting force measuring device, the strain gauge of the stress detecting sensor may be preferably disposed at an angle of approximately 45 degrees with respect to the horizontal and vertical stress center axes of or adjacent the axle and is fixedly embedded in a hole formed in or adjacent an axle at a brake caliper angle or an angle close thereto. As a result, it is possible for the stress detecting sensor to measure a road surface friction force and a normal counterforce acting one a wheel while reducing interference from other wheel-acting forces.